Air conditioning system for vehicles



March 19, 1940. c. ANDERsoN AIR CONDITIONING SYSTEM FOR VEHICLES Filed May l1, 1956 NN @QN WN QN wm.

Enz/@non Jawuc@ O. mansom Patented Mar. 19, 1940 UNITED STATES AIR CONDITIONING SYSTEM FOR VEHICLES Lawrence C. Anderson, Chicago, Ill., assignor to Pullman-Standard Car Manufacturing Company, Chicago, Ill., a corporation'of Delaware Application May 11, 1936, Serial No. 79,150

9 Claims.

This invention relates to an air conditioning system for vehicles (particularly railway passenger cars), and among the primary objects of the invention are the following: To provide an 5, auxiliary system of refrigeration whichstores refrigeration in the form of ice when the capacity of the refrigerating apparatus is not required for car cooling; and to control the auxiliary system so that there will at all times be a maximum reserve of refrigeration consistent with practical requirements for making it immediately available for car cooling when the primary system of refrigeration for any reason cuts out.

Further and other objects and advantages will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig. 1 is a schematic layout of an air conditioning system embodying the principles of this invention; and

Fig. 2 is a sectional view through the brine tank showing the temperature and pressure responsive devices for limiting the formation of ice in the tank.

Thev specific disclosure of an air conditioning system embodying the principles of this invention is for the purpose of complying with Section 4888 of the Revised Statutes, but it will be understood that the invention is not limited to the specific arrangement shown and described, and the appended claims are to be construed as broadly as the prior art will permit.

General organization The air conditioning system is adapted to be used on various classes`oi' vehicles, and the choice of a railway passenger car for illustrating an embodiment of the invention is for the most part arbitrary. There are, however, some problemsin air conditioning railway passenger cars which make the system of this invention particularly suitable for application to this class of vehicles.

The system disclosed includes means for filtering, cooling, and dehumidifying the air. The cooling of the air is accomplished by a refrigerating system which is operated through a variable speed device from one of the car axles when the car is in motion, or by a standby motor when the car is at stations. 'I'he refrigerating system includes parallel evaporator circuits, one

of which is adapted to cool the air that is'being delivered to the car interior by direct expansion coils, and the other being adapted to store up refrigeration in the .form of ice whenever car cooling is not required and there is power available for operating the refrigerating system.

Ventilation system Referring now to Fig. 1, a fragment of a railway passenger car is indicated at Ill having a" vestibule II and passenger space I2. An air duct I3 extends longitudinally of the car at roof level and has a plurality of openings I4 for distributing the conditioned, air throughout the car in- 10 terior.

Adjacent one end of the car, but still overhead isvan air conditioning chamber I5 in which the y temperature changing coils and humidifier are placed.` Air is delivered into this chamber by 15 a blower I6 whchis run from the car axle lighting system and -which draws air through a grille Il communicating with/the car interior I2, and a grille Il in the vestibule II in proportions which may be xed, at will. The fresh air that is drawn 20 in through the grille I8 in the vestibule I I passes through a filter I9 before being delivered to the air conditioning chamber.

Refrigerating equipment The refrigerating system includes a compressor 20, adapted to deliver hot gaseous refrigerant under pressure to a condenser 2I cooled by a fan 22. the rotational direction of which alternates with the direction of car movement, a receiver 30 23, in which the liquid refrigerant from the condenser 2I is stored, and parallel evaporators` 24 and 25, the former being located Within a brine tank 26, and the latter being located Within the air conditioning chamber I5 vin the path of the 35 air to be conditioned. The evaporator 24 is connected by a branch feed 21 to the main feed line 23 and by a branch return 29 to the main return line 30.' The evaporator 25, or primary coil is connected by a pipe 3| with the main feed line o 28 and by a pipe 32 with the main return line 30. v All of the refrigerating equipment with the exception of the primary coil 25 is preferably located beneath the car and the condenser is placed so that the natural draft caused by car move- 5 ment is utilized as much as possible in condensing refrigerant from the compressor.

A brine or secondary coil 33 is located in the air conditioning chamber I5 adjacent to the primary coil 25 and is connected in a fluid circuit 50 which includes the brine tank 26. A brine pump 34 is adapted to circulate brine throughv the secondary coil 33 and back again to the tank under predetermined conditions. y The pipes leading from the brine tank to the secondary coil 33 are 55 indicated at and 36, the latter terminating in a header 31 for distributing the warm brine over the evaporator coil 24, as best shown in Fig. 2.

The compressor 20 is operated through a variable speed device 38 from a car axle 39. The variable speed device includes an electro-magnetic clutch 40 and a speed control governor, generally indicated at 4|. The clutch 40 is composed of an armature 42 which is connected through a propeller shaft 43, jack shaft 44 and belt drive 45 with the axle 39, universal joints 46 being provided toaccommodate relative movement between the jack shaft 44 which is mounted on the car truck and propeller shaft 43 which is suported from the car underframe.

A field spider 41 is rotatable within the arma-- ture 42 and has a bearing surface 48 for -supporting the armature, and field coils 49 for trans# mitting torque between ,the armature 42 and spider 41 under predetermined conditions. The i spider 41 is keyed to a main speed control shaft 50 which is supported by bearings 5|, 52 and 53,

the former two bearings being enclosed withinA a speed control housing 54 mounted on the car underframe, andthe latter bearing 53 being located within the hub 55 of the armature. A belt drive 56 transmits power from the shaft 50 to the compressor. I

The current through the eld coils 49 is controlled by a fly ball governor 51 which acts through a pivoted arm 58 to change the contact pressure between silver contacts 59 mounted on springs 69 within the housing 54. 'I'he vinitial position of the silver contacts 59 is adjusted by means of a rod 6I and an adjusting nut 52, the latter bearing against a lug 38 formed on the speed control housing 54. f f

It will be observed that the direction of rotation of the shaft 50 depends upon the direction of car movement. The compressor 28 is constructed so that it operates with the same eiliciency in either direction of rotation. The condenser fan 22 which is driven by a belt 64 from the shaft 59 alternates its direction of rotation with the direction of car movement, this being desirablesince the fan acts merely to aid natural drafts in properly cooling the condenser.

Numerous valves are associated with the refrigerating system for effecting proper control ofthe system. The branch feed lines 21 and 3| leading to the evaporators 24 and 25, respectively, are controlled by solenoid valves and 86, respectively. These same lines also have expansion valves 61 and 68, respectively,y the former being set for a pressure of approximately 10 lbs. to keep the temperature of the evaporator 24 at approximately 0 F., and the latter being set at approximately 35-40 lbs. for effecting a temperature of approximately 4045 F'.,

in the primary coil 25. At this temperature, the

coil 25 will dehumidify the air that is being passed through the coil. The lower temperature of the coil 24 makes it desirable to employ a heat exchanger 89 betweenthe return line 29 and the feed line 21.

A check valve 19 in the branch return line 29 associated with the brine tank evaporator 24 prevents liquid from condensing in the brine tank evaporator when the primary coll 25 ls in operation.

An alternating current standby motor 1| (220 volts, or 440 volts) is vprovided for driving the compressor when the car is at stations, the drive being effected through a shaft 12 which in effect is a continuation of the speed control shaft 50.

Freon is preferably used as the refrigerant for the system.

Control of refrigerating system control circuits until the car reaches its destination.

The car axle-generator-battery lighting unit consists of a generator 80, the armature 8| of which is driven through a belt drive 82 from a car axle 83, this axle being at the opposite end of the car from the axle 39. The field 84 of the generator is controlled by a generator regulator which includes a carbon pile 85 connected in series with the field, and a carbon pile control solenoid 86, the coil of which is connected across the armature terminals. A spring 81 applies a given pressure to the carbon pile 85 as long as no current flows through the coil of the solenoid 86. This pressure is gradually diminished as current flows through the coil of the solenoid 86. As pressure on the carbon pile 85 is reduced, less current flows through the field 84 and the output of the generator is thereby held at a substantially constant value.

'The positive terminal 88 of the generator is connected through a conductor 89, battery cut-in switch 99 and conductor 9| with the positive terminal 92 of a battery 93 and the negative terminal 94 of the generator is connected to the negative terminal 95 of the battery through conductors 96 and 91.

The battery cut-in switch 90 closes the connection between the positive terminals of the generator and battery as soon as the voltage across the positive and negative terminals of the generator is sufficient to cause the coil 98of the battery cut-in switch to pull down the armature 99. As soon as this has been accomplished, a holding coil |89 keeps the armature down until the voltage across the generator is insuillcient to resist the tension of the spring |0|, whereupon the generator and battery-are disconnected.

The generator 89 is equipped with 4a pole changer for preserving the polarity of the generator irrespective of the direction of car movement. A description of the pole changer may be found in Car Builders Cyclopedia, 1931 (published by Simmons-Boardman Publishing Company) at pages 678 and 679.

'I'he battery 93 may be of standard size and capacity which is generally 450-600 amperehour capacity.

In the particular embodiment of the invention herein shown and described, the primary coil 25 is maintained-in operation as long as car cooling is required, and thereafter, if the compressor is still in operation, the refrigeration load is transferred to the evaporator coil 24 in the brine tank 25. After a suiilcient amount of ice has been built up in the brine tank, as determined by a submerged thermostat |02 and a pressure responsive device |93, the compressor is shut off.

The brine pump 34, which is,rotated by a motor |94, is operated automatically as soon as the car speed falls below a predetermined minimum. In the particular system 'shown in the drawing, the starting of the brine pump autolowered by a coil l5.

matically stops the primary system of refrigeration which includes circulation of refrigerant through the primary coil 25. This, however, is optional for by very slight modification of the system shown in the drawing, it is possible to have the brine pump circulate cold brine at low car speeds to assist the primary system which, at low car speed, is operating at fractional capacity.

A cooling thermostat located adjacent to the re-circulated air intake |1 controls the position of a cooling relay, generally designated |06, the armature 01 of which is normally held in its raised position by a spring |08, but which is |09 whenever the circuit through the cooling thermostat |05 is closed. The circuit for lowerirg the armature |01 may be traced from thel positive terminal 92 of the battery through a conductor I, coil |09, conductoei` H2, thermostat |05, conductor ||3, and back to the negative terminal 95 of the battery through conductor ||4.

Let us rst assume that car cooling is called for, and that the armature |01 is in its lowered position. Under these conditions, the arm H5 of the cooling relay will bridge contacts ||6 and ||1, the arm ||8 will bridge contacts ||9 andI |20, andthe arm |2| will bridge contacts |22 and |23. l

It will be noted that contacts ||1, |20, and |23v are all connected t0' the positive side of the battery 93 through the conductor I. The bridging of contact ||1 with contact ||6, therefore, closes one side of the circuit through the brine pump motor |04 and makes its operation subject to the action of the speed control brine switch, generally designated |24, as will be seen by tracing this circuit from the contact ||6 through conductor |25, motor |04, conductor |26 to the speed control switch |24. This switch operates with a snap action and has its arm |21 connected by a conductor |28 to the negative terminal 95 of the battery 93. When the speed of the car has been reduced to such an extent that the iiy ball governor 51 has been forced by the the primary system of refrigeration is in operation.

Assuming this last condition, and that the thermostat |05 still calls for air cooling, the bridging of contacts |20 and ||9 closes the circuit through the solenoid valve 66 in the branch feed line 3| leading to Vthe primary coil 25, as will be seen by tracing the circuit from the contact |20 through contact H9, conductor |32, solenoid `valve 66, conductor |33, and conductor ||4 -back to the negative side of the battery. The

' energization of solenoid valve 66 opens the branch vfeed line 3| .and permits refrigerant to be ex- 'panded-'in-the coil 25, thus cooling the car.

The 'closing -of ,thermostat |05 and the consequent energization of thecoil, |09 also has the |20 and |I1, is connected directly to the positive side of a battery 93) through the arm 2| attached to the armature |01, contact |22, conductor |34, conductor |35, switch blade |36 of the alternating current switch generally designated |31 (the switch arm |36 closes the contacts field coils 49 is fully explained in the patent toI Anthony Winther No. 1,982,461, issued November 27, i934, and reference is made to that patent for more specific disclosure of this apparatus and its method of functioning.

Thus far, we have assumed that the car thermostat |05 calls for cooling. Now let us assume that no further cooling is needed within the car.

Under these circumstances, the coil |09 is de-energized and the spring |08 of the cooling relay has pulled the armature |01 to the position shown in Fig. 1 of the drawing. In this position, the arm ||5 of the armature bridges contacts |60 and |6|, and the arm |2| bridges the contacts |62 and |63. Contacts |60 and |62 are connected through a conductor |64, the pressure responsive device |03, thermostat |02 (the pressure responsive device |03 and the thermostat |02 being connected in parallel) conductor |65 and conductor to the positive side of the battery 93.

The bridging of contacts |60 and I6| therefore v closes the circuit throimh the solenoid valve 65 in the branch feed line 21 leading to the brine tank evaporator'24, unless both the pressure responsive device |03 and the ice thermostat |02 have opened their respective circuits and unless the speed of the car is such that the switch arm |21 has been snapped to the position shown in the drawing, i. e. in Contact with contact |30. This means that the owof refrigerant to the brine tank evaporator 24 is stopped either when suilicient ice has been formed (as determined by the pressure device |03 and thermostat |02), orA

when the car is travelling at such a low speed that the refrigerant compressor has not suiiicient capacity to do any useful work in building up ice within the lbring tank 26. The circuit can be traced from the contact through the arm ||5, contact |6|, conductor |66, solenoid valve 65, conductor |61, contact |3|, switch arm |21 and back to the negative side of the battery through conductor |28. i

The bridging of contacts |82 and |63 by the arm |2|A closes the circuit through the speed control mechanism andthus operates the compressor from the car axle 39, but it will be understood that the energization of the speed control mechanism in this case is subject to the action of the pressure responsive device |03 and thermostat |02 associated with the brine tank evaporator 24 since these two devices are connected in series with the contacts |62 and |63.

The check valve 10 prevents the refrigerant from condensing in the brinev tank evaporator 24 when the primary coil 25 is in operation. This` is necessary because the two coils are being operated at different suction pressures.

At stations where three phase alternating current is available, a connection is made at the receptacle |15 with the A. C. source, the plug |16 having a contactor |11 for bridging the contacts |18 and |19 in the receptacle and thus completing the direct current circuit through the coil |80 of the alternating current switch |31, provided the thermostat |05 has lowered the armature |01 of the cooling relay to bridge the contacts |22 and |23. The contacts for the three phase current are arranged in the receptacle so that they connect with the alternating current source before the conductor |11 bridges the contacts |18 and |19, so that the closing of the circuit for the energization of the alternating current motor 1| takes place in the alternating current switch |31 where the contacts are suitably constructed for taking the load. It will be observed that when the coil |80 is energized, the arm |36 of the armature |8| breaks the circuit between contacts |38 and |39 before the A. C. motor circuit is completed which means that the eld coils 48 of the speed control mechanism 38 are deenergized, and, therefore, cause no drag as the shaft is rotated by the motor 1|.

The control of the refrigerating system by the cooling relay |06 is the same when the alternating current motor`1| is in operation as when the Compressor is powered through the speed control device 38. The primary coil 25 is supplied with refrigerant as long as car cooling is required and, thereafter, the compressor capacity is utilized for building up ice in the brine tank 26 until the pressure responsive device |03 and ice thermostat y||l2 open the circuit through the coil |80 and thus stop the alternating current motor 1|.

A low pressure safety switch 200 is associated with the main suction line 30 leading to the compressor and itsfunction is to shut off the compressor when the pressure in the suction line drops below a predetermined minimum. The switch has'two sets of contacts, one set being interposed in the series with the A. C. switch coil |80 so as to open the A. C. switch in case the compressor is being driven by the motor 1|, and the other set is interposed in the conductor |34 to open the circuit through the speed control device 40 in case the compressor is being driven from the car axlef Summary of cooling system A. When the car is travelling above a predetermined minimum speed and the cooling thermostat |05 calls for cooling, the following takes place:

1. The brine pump 3Lis placed in readiness for operation whenever the car speed falls below the predetermined minimum speed. (The switching on of the brine pump may be concurrent with the shutting off of the compressor due to low carspeed, as shown in the drawing, or there may be an overlap.)

2. The solenoid valve 66 which controls the flow of refrigerant to the primary coil 25 in the air conditioning chamber |5 is energized, thus allowing refrigerant to flow tothe coil and cool the air that is being delivered into the car.

3. The speed control circuit is energized so that torque is transmitted from one of the car axles through the speed control mechanism to the compressor for operating the refrigerating system.

B: When the cooling thermostat |05 does not call for car cooling (the car still travelling above the predetermined minimum speed), the following action takes place:

1. The solenoid valve which controls the flow of refrigerant to the brine tank evaporator 24 is energized, thus allowing refrigerant to flow to this evaporator (solenoid valve 66 being deenergized and, therefore, closed) but (a) If the sufficient ice has been formed to encase the bulb |68 of the ice, thermostat, (see Fig. 2) there will be a quick drop in temperature which will actuate the ice thermostat |02 and open the shunt circuit which is controlled by it, but the compressor is not shut off until the pressure re sponsive device |03 has also been actuated to open its shunt circuit.

(b) If the pressure in the evaporator coil 24 falls below a predetermined minimum, it will actuate the pressure responsive device |03 and open the shunt circuit which it controls, but the compressor is not shut off unless the thermostat |02 has indicated that ice has formed about the bulb |88.

'Ihe combination of temperature and pressure control of the ice formation in the brine tank is exceedingly desirable because neither one alone is capable of effecting the proper control. As it is, when the ice formation reaches a predetermined amount, the pressurein the suction line drops sufliciently to actuate the pressure responsive device |03 and shut off the compressor. (The pressure responsive device is set so that the ice thermostat will also open its branch of the circuit before the pressure responsive device operates to open the circuit.)

As soon as the compressor stops, the pressure in the brine evaporator coil 24 rises to a pressure which corresponds to the temperature of the ice in the tank and so obviously the cut-in pressure of the pressure responsive device |03 must be above this valve. Unfortunately, however, if the cut-in pressure is but slightly higher than the balancing pressure, the compressor will cycle too frequently for efficient operation, and if the cut-in pressure is substantially higher than the balancing pressure almost all of the ice in the tank will be melted before the compressor again begins to build up more ice.

'I'he ice thermostat on theother hand, is capable of starting the compressor at the proper time because it, in effect, measures'the extent of the ice formation. When brine is being circulated through the coil 33, the warm brine entering the tank through the spray pipe 31 melts the upper layer of ice, and as soon as sufficient ice has been melted to uncover the thermostat bulb |68, the thermostat |02 operates to close the circuit through the compressor and again begin the manufacture of ice.

'I'he ice thermostat is not capable in itself of effecting the complete control (without the pressure responsive device |03) because if the thermostat is located in a position such as shown in Fig. 2, the compressor will go on and off too frequently for eilicient operation of the system.

The operation of the ice thermostat |02 and the pressure responsive device |03 may, therefore, be summarized as follows:

Assuming a full tank of ice, the rst thing that happens when the ice begins to melt in any substantial amount is that the ice thermostat bulb |68 is uncovered, thus closing the circuit through the thermostat |02 and opening the refrigerant valve 65. The onrush of refrigerant into the coil 24 raises the pressure within the coil a sufcient amount to close the circuit through the pressure responsive device |03 (this is not necessary for having the compressor operate). The

formation of ice continues until the pressure in the coil drops to the cut-out pressure of the pressure responsive device |03 and then the compressor is shut off.

Stated in other words, the ice thermostat |02 serves to start the compressor whenever a portion of the ice hasbeen melted at the top of the tank and requires replenishing and the pressure responsive device |03 serves to stop the compressor when the desired amount vof the ice has been formed.

2. The speed control circuit is energized to run the compressor by power taken from the car axle, but this circuit also is subject to the conditions (a) and (b) above. In other words, as long as car cooling is not required, and there is suflicient refrigerant capacity to do useful work, and provided further that the reserve refrigeration in the brine tank 26 is below a predetermined amount, refrigerant will ow to the evaporator 2d, but when sufcient ice has been formed as determined by both the surface condition and average condition, the ow of refrigerant to the brine tank evaporator 24 will be stopped, and the speed control circuit de-energized.

C. When the car is travelling below the predetermined minimum speed and the car thermostat |05 calls for cooling, the brine pump 3l is started and car cooling is effected by the secondary coil 33. At the same time, solenoid valves 65 and 66 are de-energized and hence closed, thus shutting olf the supply of refrigerant to both coils (24 and 25).

D. When the car is travelling at a speed so slow that the snap switch |24 is in the position shown in Fig. 1 and at the same time the car thermostat |05 does not call for cooling, the entire refrigeration system is inactive.

E. When the car is at stations where there is an alternating current source of electrical energy and the car thermostat |05 calls for cooling, the control of the refrigeration system is the same as described under point A of this summary, with the exception that the coil of the A. C.

I switch |31 is energized instead of the speed control mechanism.

F. When the car is at stations where there is an alternating current source of electrical energy available and the car thermostat |05 does not call for car cooling, the control of the refrigeration system is the same as described under point B of this summary with the exception that the shutting oif of the compressor when sufficient ice has been formed in the brine tank is effected by deenergizing the coil |00 of the A. C. switch |31 instead of opening the circuit through the speed control mechanism.

It will be noted that the check valve in the suction line of the holdover evaporator has an important bearing on the operation of the temperature-pressure control for holdover cooling, fr unless the check valve or its equivalent be used, the pressure in the holdover coil would quickly rise to a point sufficient to operate the pressure switch, and, as a result, the holdover tank would be calling for cooling even though there were a suicient amount of ice in the tank.

It will be understood that since the pressure and temperature switches are connected in parallel, either one is capable of energizing the compressor circuit, but both must be open before the compressor circuit will be rendered ineffective.

I claim:

1. In a refrigerating system, an evaporator, a compressor` for supplying liquid refrigerant to the evaporator, a source of power for said compressor, a congealable liquid surrounding the evaporator, and means for controlling the operation of the compressor to build up and maintain a predetermined amount of refrigeration in the liquid, said means including a thermostatic device for starting the compressor, and a pressure responsive device for stopping the compressor, said thermostatic and pressure responsive devices being connected in parallel.

2. In a refrigerating system, an evaporator, a compressor for supplying liquid refrigerant to the evaporator, a source of power for said compressor, a congealable liquid surrounding the evaporator, means for circulating said liquid in a uid circuit which includes a heat exchange coil, and means for controlling the operation of the compressor so as to build up and maintain a predetermined amount of the refrigeration in the Lquid surrounding the evaporator, said means comprising an ice thermostat located in the liquid surrounding the evaporator and adjacent to the place where the fluid returning from the heat exchanger first makes contact with the evaporator or the ice formed thereon, and a pressure responsive device associated with the evaporator having cut-in and cut-out pressures bearing such relation to the corresponding values of the ice thermostat that the ice thermostat will always function to start the compressor but will be inefiective to stop the compressor, and the pressure responsive device will always function to stop the compressor butAwill be ineffective to start the Compressor.

evaporator, a source of power for said compressor, a congealable liquid surroundingl the evaporator, and means for shutting off the compressor after a predetermined amount of refrigeration has been stored in the liquid, said means including a switch responsive to pressure in the suction line of the evaporator coil, and a switch responsive to the temperature at a given point in the congealable liquid, said switches being so arranged with respect to each other that the lastnamed switch is adapted to place the compressor back into operation without the aid of the firstnamed switch.

4. In a refrigerating system, an evaporator, a compressor for supplying liquid refrigerant to the evaporator, a source of power for said compressor, a congealable liquid surrounding the evaporator, and means for shutting oif the compressor after a predetermined amount of refrigeration has been stored in the liquid, said means including switches responsive to the pressure in the suction line of the evaporator and the temperature at a given point in the congealable liquid, said switches being so arranged with respect to each other that the temperature responsive switch is adapted to place the compressor back into operation wthout the aid of the pressure-responsive switch.

5. In a refrigerating system, an evaporator, a compressor for supplying liquid refrigerant to the evaporator, a source of power for said compressor, a congealable liquid surrounding the evaporator, and means for shuttingI oif the compressor after a predetermined amount of refrigeration has been stored in the liquid, said means including switches responsive to the pressure in the suction line of the evaporator and the temperature at a given point in the congealable liquid, and an electrical circuit associated with the switches and with the source of power for the compressor for de-energizing the latter only when the circuit through both switches is open.

6. In a refrigerating system, a high temperature evaporator, a low temperature evaporator connected in parallel with the high temperature evaporator, a congealing tank in WDich'the low temperature evaporator is mounted, means for supplying refrigerant alternatively to said evaporators, said means including a device responsive to the pressure in the low temperature evaporator, a thermostat in the congealing tank, and a check valve in the suction line of the low temperature evaporator.

'7. In anair conditioning system i'orI railway cars, a refrigerant compressor, a drive for the compressor, a primary system of-refrigeration adapted to make use of the full capacity of the compressor whenever the primary system is, required for cooling the car, a secondary system of refrigeration including a tank of relatively small diameter containing a relatively large evaporator and a congealing solution, means for throwing the full capacity of the compressor to the evaporator whenever the primary System is not in operation, and means for controlling the flow of refrigerant to the evaporator in the tank, said last named means including a switch responsive to pressure in the suction line of the evaporator coil, and a switch responsive to the temperature'at a given point in the congealable liquid.

8. In a refrigerating system, an evaporator, a compressor for supplying liquid refrigerant to the ajenos@ evaporator. a Source of power for said conipressory a congealable liquid surrounding the evaporator, and-means for governing the ilow of refrigerant to the coil to control the formation of ice thereon, said means including switches 'responsive to the pressure in the -suction line of the evaporator and the temperature at a given point in the congealable liquid, said temperature switch being arranged to start the ilow of refrigerant to the coil, and said pressure responsive switchY being arranged to have exclusive control over the stopping -of the now of refrigerant to thecoil.

9. InV an air conditioning system for enclov sures, a primary system of refrigeration including a source of volatile refrigerant and a direct expansion coll in the path of air to be conditioned, a secondary system of refrigeration including the :same source of refrigerant, a brine tank, an evaporator in, the brine tank connected in parallel with the'l direct expansion coil, a brine coil in the pathof air to. be conditioned, and a fluid circuit between the brine tank and brine coil, means responsive to temperature conditions within the enclosure for selecting which evaporator coil is to receive refrigerant from said source, and means irigerant is permitted to enter the brine evapo- .f

rator.

LAWRENCE Cn ANDERSON. 

